A variety of pump action firearms are known. One variety of pump action firearms are Mossberg pump action shotguns manufactured by O.F. Mossberg & Sons, Inc., which include the model 500, 835 and 590 pump action shotguns, among others. Each of these models of the Mossberg pump action shotgun are of the same basic configuration and include a barrel with a magazine tube arranged adjacent and parallel thereto extending from a receiver. An action slide assembly is axially received on the magazine tube and includes a pair of action bars which are received in the receiver. The action bars are attached to the action slide assembly in a manner permitting some pivoting about a horizontal axis at the point of attachment. The standard Mossberg 500, 835 and 590 model pump action shotguns further include a forend consisting of an elongate body having a U-shaped cross-section and an integrally formed internal frame which axially receives the slide action assembly. The top portion of the internal frame defines a pair of angled shelves. These angled shelves are configured so that with the forend axially received on the slide action assembly and with the forend attached to the slide action assembly by an action slide tube nut threadably engaging a threaded distal end of the action slide assembly, the angled shelves snuggly nest the outer diameter of the barrel which overlies the magazine tube. The slide action assembly is slid along the magazine tube to chamber a round by action of the action bars within the receiver. Because the action bars of the action slide assembly are pivotably attached to the action slide assembly as discussed above and because the action bars are relatively flexible members, a close tolerance between the angled shelves and the barrel is necessary to limit rotation of the forend about the magazine tube axis relative to the barrel. Typically the barrel is at least slightly tapered from a larger diameter at the receiver to a narrower diameter near distal end. Ideally the angled shelves touch the barrel at least when the forend is near the receiver and the proximal end of the barrel. Rotation of the forend about the magazine tube is highly undesirable as it can overstress the action bars with prolonged use and can cause the forend to have a sloppy feel during actuation.
One problem with the design of the forend for the Mossberg 500, 835 and 590 model pump action shotguns is that barrels with different outer diameters at the receiver and the distal end may be used with the various models. As a result, in order to maintain an acceptable tolerance between the angled shelves of the forend and various barrels of different outer diameter at the receiver and the distal end used with the respective models, a distinct forend having angled shelves configured to nest a particular barrel outer diameter profile must be used with each barrel having a different outer diameters at the receiver and distal ends so as to limit relative rotation between the forend and the barrel. As a result, Mossberg and providers of after-market forends compatible with Mossberg pump action shotguns must provide different forends for each different diameter profile of the barrels compatible with the different Mossberg models or hazard a sloppy feel of the forend.
The present invention is directed toward overcoming one or more of the problems discussed above.